1. Field of the Invention
The present invention relates to an electric double layer capacitor.
2. Related Background Art
In recent years, with a higher power of electronic equipment, an improvement in the working voltage of an electric double layer capacitor as a power supply has been attempted. A method for connecting a plurality of cells in series is proposed as one method for improving the working voltage of an electric double layer capacitor (for example, see Japanese Patent Laid-Open No. 2000-208378). Japanese Patent Laid-Open No. 2000-208378 discloses an electric double layer capacitor in which a plurality of capacitor elements are surface-contacted via a conductive rubber sheet, contacted in series, and housed in a metal case.
In an electric double layer capacitor using cells connected in series in this manner, when variations in the holding voltage of individual cells occur, overcharged cells degrade with charge and discharge cycles, thereby, the life of the entire electric double layer capacitor may degrade. Therefore, the suppression of such variations in the holding voltage of cells is studied (for example, see Japanese Patent Laid-Open No. 2002-142369). Japanese Patent Laid-Open No. 2002-142369 discloses an electric double layer capacitor that suppresses variations in holding voltage caused by a difference in leakage current between individual cells.